[PATCH 2/2][SRU][ARTFUL] block: cope with WRITE ZEROES failing in blkdev_issue_zeroout()

[Colin Ian King]

On 05/01/18 15:22, Kleber Souza wrote:
> On 11/21/17 18:05, Colin King wrote:
>> From: Ilya Dryomov <idryomov at gmail.com>
>>
>> BugLink: https://bugs.launchpad.net/bugs/1726818
>>
>> sd_config_write_same() ignores ->max_ws_blocks == 0 and resets it to
>> permit trying WRITE SAME on older SCSI devices, unless ->no_write_same
>> is set.  Because REQ_OP_WRITE_ZEROES is implemented in terms of WRITE
>> SAME, blkdev_issue_zeroout() may fail with -EREMOTEIO:
>>
>>   $ fallocate -zn -l 1k /dev/sdg
>>   fallocate: fallocate failed: Remote I/O error
>>   $ fallocate -zn -l 1k /dev/sdg  # OK
>>   $ fallocate -zn -l 1k /dev/sdg  # OK
>>
>> The following calls succeed because sd_done() sets ->no_write_same in
>> response to a sense that would become BLK_STS_TARGET/-EREMOTEIO, causing
>> __blkdev_issue_zeroout() to fall back to generating ZERO_PAGE bios.
>>
>> This means blkdev_issue_zeroout() must cope with WRITE ZEROES failing
>> and fall back to manually zeroing, unless BLKDEV_ZERO_NOFALLBACK is
>> specified.  For BLKDEV_ZERO_NOFALLBACK case, return -EOPNOTSUPP if
>> sd_done() has just set ->no_write_same thus indicating lack of offload
>> support.
>>
>> Fixes: c20cfc27a473 ("block: stop using blkdev_issue_write_same for zeroing")
>> Cc: Hannes Reinecke <hare at suse.com>
>> Reviewed-by: Christoph Hellwig <hch at lst.de>
>> Reviewed-by: Martin K. Petersen <martin.petersen at oracle.com>
>> Signed-off-by: Ilya Dryomov <idryomov at gmail.com>
>> Signed-off-by: Jens Axboe <axboe at kernel.dk>
> 
> Hi Colin,
> 
> This patch is missing the "backported/cherry picked from" tag and your SOB.

Do you mind adding the following lines before applying patch:

(cherry picked from upstream commit
d5ce4c31d6df518dd8f63bbae20d7423c5018a6c)
Signed-off-by: Colin Ian King <colin.king at canonical.com>

> 
> The first patch of the series has you as the author, but mainline commit
> 425a4dba7953e35ffd096771973add6d2f40d2ed has "Ilya Dryomov
> <idryomov at gmail.com>" as author. This we can fix when applying the
> patch, but the SOB for the second one needs to come from you.
> 
> Thanks,
> Kleber
> 
>> ---
>>  block/blk-lib.c | 45 +++++++++++++++++++++++++++++++++++----------
>>  1 file changed, 35 insertions(+), 10 deletions(-)
>>
>> diff --git a/block/blk-lib.c b/block/blk-lib.c
>> index 4ef942c..595517c 100644
>> --- a/block/blk-lib.c
>> +++ b/block/blk-lib.c
>> @@ -321,12 +321,6 @@ static int __blkdev_issue_zero_pages(struct block_device *bdev,
>>   *  Zero-fill a block range, either using hardware offload or by explicitly
>>   *  writing zeroes to the device.
>>   *
>> - *  Note that this function may fail with -EOPNOTSUPP if the driver signals
>> - *  zeroing offload support, but the device fails to process the command (for
>> - *  some devices there is no non-destructive way to verify whether this
>> - *  operation is actually supported).  In this case the caller should call
>> - *  retry the call to blkdev_issue_zeroout() and the fallback path will be used.
>> - *
>>   *  If a device is using logical block provisioning, the underlying space will
>>   *  not be released if %flags contains BLKDEV_ZERO_NOUNMAP.
>>   *
>> @@ -370,18 +364,49 @@ EXPORT_SYMBOL(__blkdev_issue_zeroout);
>>  int blkdev_issue_zeroout(struct block_device *bdev, sector_t sector,
>>  		sector_t nr_sects, gfp_t gfp_mask, unsigned flags)
>>  {
>> -	int ret;
>> -	struct bio *bio = NULL;
>> +	int ret = 0;
>> +	sector_t bs_mask;
>> +	struct bio *bio;
>>  	struct blk_plug plug;
>> +	bool try_write_zeroes = !!bdev_write_zeroes_sectors(bdev);
>>  
>> +	bs_mask = (bdev_logical_block_size(bdev) >> 9) - 1;
>> +	if ((sector | nr_sects) & bs_mask)
>> +		return -EINVAL;
>> +
>> +retry:
>> +	bio = NULL;
>>  	blk_start_plug(&plug);
>> -	ret = __blkdev_issue_zeroout(bdev, sector, nr_sects, gfp_mask,
>> -			&bio, flags);
>> +	if (try_write_zeroes) {
>> +		ret = __blkdev_issue_write_zeroes(bdev, sector, nr_sects,
>> +						  gfp_mask, &bio, flags);
>> +	} else if (!(flags & BLKDEV_ZERO_NOFALLBACK)) {
>> +		ret = __blkdev_issue_zero_pages(bdev, sector, nr_sects,
>> +						gfp_mask, &bio);
>> +	} else {
>> +		/* No zeroing offload support */
>> +		ret = -EOPNOTSUPP;
>> +	}
>>  	if (ret == 0 && bio) {
>>  		ret = submit_bio_wait(bio);
>>  		bio_put(bio);
>>  	}
>>  	blk_finish_plug(&plug);
>> +	if (ret && try_write_zeroes) {
>> +		if (!(flags & BLKDEV_ZERO_NOFALLBACK)) {
>> +			try_write_zeroes = false;
>> +			goto retry;
>> +		}
>> +		if (!bdev_write_zeroes_sectors(bdev)) {
>> +			/*
>> +			 * Zeroing offload support was indicated, but the
>> +			 * device reported ILLEGAL REQUEST (for some devices
>> +			 * there is no non-destructive way to verify whether
>> +			 * WRITE ZEROES is actually supported).
>> +			 */
>> +			ret = -EOPNOTSUPP;
>> +		}
>> +	}
>>  
>>  	return ret;
>>  }
>>
>